Research shall be continued or initiated in the following areas: (1) On the properties and mechanisms of action of 2-keto-4-hydroxyglutarate aldolase, an important enzyme in the metabolism of L-hydroxyproline by mammals which has been found to differ in many respects from other aldolases studied so far. We have the enzyme in highly purified form from extracts of bovine liver and are attempting to purify it from bovine kidney. This adolase is also present in E. coli; homogeneous samples of the enzyme are routinely prepared from this source. Our efforts include an examination of the subunit structure of the enzyme, an exploration of the functional groups in the enzyme molecule which participate in the catalytic process, isolation of active-site peptides, and the establishment of structure-function relationships in general. Comparative enzymology is done. (2) On the nature of new reactions and enzymes in the metabolism of gamma-hydroxyglutamic acid, an intermediate in L-hydroxyproline degradation by mammals. (3) On the purification, properties, and role of L-threonine dehydrogenase and D-1-amino-2 propanol: NAD oxidoreductase, enzymes found in animals and bacteria that are involved in the catabolism of L-threonine. These two exzymes also have the potential role of providing the D-1-amino-2 propanol moiety utilized in vitamin B12 biosynthesis by bacteria. BIBLIOGRAPHIC REFERENCES: Hansen, B.A. and Dekker, E.E. (1976) Inactivation of Bovine Liver 2-Keto-4-hydroxyglutarate Aldolase by Cyanide in the Presence of Aldehydes. Biochemistry, 15, 2912-2917. Wang, J.K. and Dekker E.E. (1976) Subunit Structure of E. coli 2-Keto-4-hydroxyglutarate Aldolase. Federation Proc., 35, 1521